Fall officially kicks off on the equinox this weekend

While weatherpeople begin counting fall at the start of September, the seasons have official starts based on astronomy as well. The Autumnal Equinox this weekend marks a day of equal daylight and nighttime.

The equinox occurs when the Earth's tilt is neither facing toward nor away from the sun. This is what brings equal day and night to all parts of the Earth's surface. Then, into the fall and winter the days get shorter and temperatures cool as the northern hemisphere tilts away from the sun.

You might have heard that the Earth is closer to the Sun during the winter than in summer. This is true when considering Earth's elliptical (oval-shaped) orbit, the planet is not circling the sun in a perfect circle. However, even as Earth gets closer to the sun in winter, the tilt of the Earth away from the sun is enough to offset this and bring us cold winters.